1. Field of the Invention
The present invention relates generally to an external fixator for use in orthopedic surgical applications. More particularly, the present invention relates to a ring system for external fixation of bone and a related method.
2. Discussion of the Related Art
In various orthopedic surgical procedures, it is necessary to secure two bone portions in a relatively fixed relationship to each other. For example, the need for establishing such a secured relationship is often a result of a fracture which has occurred to the bone. To ensure that the bone can regenerate in the proper orientation and fuse the fracture, it is important that the bone portions be fixed in their desired positions during bone regeneration.
Various external fixation devices for the repair of traumatized bone are known. For example, U.S. Pat. No. 5,662,650 to Bailey et al. discloses an apparatus for the external fixation of large bones. The apparatus is illustrated to include a main body as well as a first and second bone screw clamps. The main body serves to allow the apparatus to axially rotate, thereby providing a proper longitudinal rotational location of the bone screws with respect to a bone. The first bone screw clamp is used to secure a first pair of bone screws to the apparatus while permitting the first pair of bone screws to be axially displaced from the main body. In a similar fashion, the second bone screw clamp functions to secure a second bone screw to the apparatus and to allow the second bone screw to be axially displaced with respect to the main body. U.S. Pat. No. 5,662,650 is incorporated by reference as if fully set forth herein.
In certain orthopedic surgical procedures, it is known to employ a ring assembly which encircles a bone and is securely attached thereto with tension wires. For example, U.S. Pat. No. 4,784,125 to Monticelli, et al. discloses an external fixation system incorporating a pair of rings adapted for independent securement to a bone. The external fixation system contains a plurality of threaded rods connecting the two rings, thereby providing flexibility in inserting bone screws and an ability to distract the bone.
While known external fixation systems incorporating rings for surrounding a bone have proven to be suitable for certain applications, they are all associated with disadvantages. In this regard, known external fixation systems of the type shown in U.S. Pat. No. 4,784,125 require independent rotation of multiple threaded connecting rods to facilitate bone distraction. In addition, known ring systems for external fixation typically allow for wire fixation only at fixed points above or below one of the rings. The optimal location to secure a wire may not be at one of these fixed points and it may be difficult to offset the ring from the joint space.